Laser blown fuses historically have been used in logic processes for memory redundancy control and die identification. In some technologies the laser blown fuses are being replaced by electrically programmable fuses. An electrical programmable fuse cell contains an electrically programmable element and sense circuit such that its output may be permanently set to a logic `1` instead of its natural unprogrammed state, a logic `0` or vice-versa. These electrically programmable fuse cells could be used for not only memory redundancy control and die identification, but also for analog trimming control, customer owned configuration bits, encryption key coding, in addition to a variety of other applications.
Presently, electrically programmable fuses have to be customized to a particular application. For example, if a manufacturer wants to provide a set of write protected fuses for die identification, the manufacturer will integrate the fuses into a design and provide a probe pad that is not coupled to an external pin when the wafer is packaged into an integrated circuit. This prohibits the customer from overwriting the fuse data. Customer specific fuses will then be provided via a separate pin on the integrated circuit for programming by the customer. In another situation, a manufacturer may want to provide fuses with confidential information for use by the device within which the fuses have been integrated. The manufacturer would have to fabricate custom fuses into the device that include outputs accessible to circuitry within the device and not the customer to provide read protection of the information. Although this has been sufficient for programming a limited number of electrically programmable fuses, it becomes quite cumbersome when programming a large number of electrically programmable fuses across different devices that may be integrated into a single integrated circuit. In addition, providing multiple pads and pins wastes die and board space. Furthermore, in certain applications, such as calibration, it is undesirable to be limited to either a pad or pin programming method because of changes in parameters from the wafer stage to the package stage.
The present art has not provided an electrically programmable fuse arrangement that provides the manufacturer and customer with read protect, write protect, and test capabilities. The present art also has not provided an electrically programmable fuse arrangement that can be utilized across multiple devices in a large scale application, while allowing for either pin or pad access programming. Accordingly, there is a strong need in the art for a system and/or method for providing a programmable electrical fuse device that allows for write and/or read protection across a variety of different applications.